This invention relates to glue applicator assemblies of the type used to apply liquid glue to sheet material, such as to blanks which are ultimately formed into paper boxes. More particularly, the invention relates to a glue applicator roll assembly for a gluer.
Various prior art glue applicator equipment has been developed for the purpose of feeding sheets of material in sequence to a series of processing stations and coating the sheet material with glue and other liquids at one of the processing stations. These machines typically include equipment for picking off the end sheet from a stack of sheet material, feeding the sheet along a path generally parallel to the plane of the sheet material past a rotating cylindrical glue applicator roll, and then to various subsequent work stations. The glue applicator roll usually continuously rotates in contact with another wetting roll which is partially submerged in a body of liquid glue or other liquid. As the system operates, the liquid glue tends to accumulate and harden on the various parts of the processing equipment, particularly on the end portions of the glue applicator roll. The accumulation of glue at the ends of the glue applicator roll is undesirable, particularly because an accumulation of glue tends to interfere with the proper continuous operation of the equipment.
Various wiper blades and other devices have been used in the past to scrape or wipe glue from the cylindrical glue applicator roll. The typical prior art wiper blades have been positioned at the ends of the glue applicator roll by mounting the wiper blades on the pick finger support bar which is usually located above the cylindrical applicator roll and which is in a convenient location for mounting the wiper blades or by supporting the wiper blades form the bearing blocks at the ends of the glue applicator roll. The pick finger support bar supports a plurality of pick fingers which are arranged across the length of the glue applicator roll and which function to wedge the sheet material away from the glue applicator roll and guide the sheet material along its processing path toward the next work station. It is important that the pick fingers have their pointed ends in close juxtaposition with respect to the curved surface of the cylindrical glue applicator roll so as to properly pick the sheet material away from the roll instead of allowing the sheet material to pass between the pick fingers and the glue applicator roll. Any vibrations or other external forces imparted to the pick support bar tends to disrupt the positions of the pick fingers, causing the pick fingers to allow the sheet material moving with the cylindrical glue applicator roll to pass beneath the pick fingers and therefore jam the equipment.
The prior art pick finger support bars have been supported at their ends adjacent and parallel to the cylindrical glue applicator roll. The prior art structure used to support the pick finger support bar tends to cause the pick finger support bar to bow or bend downwardly at its center portion. The amount of curvature in the bow varies, depending upon the force applied at the ends of the pick finger support bar. For example, one prior art structure comprises slots formed in the end bearing blocks of the equipment, and internally threaded bore extending through each end of the pick finger support bar, and elevational screws threaded through the bores for engagement with the bottom of the slots. The machine operator is able to adjust the height of the ends of the pick finger support bar by rotating the elevation screws to raise or lower the ends of the bar. After the ends of the bar have been properly located, the prior art assembly included a means for clamping the end portions of the middle portion of the bar downwardly into the slots to hold the bar at its ends. This downward clamping force tends to bow the bar downwardly, with more force at the ends causing a larger bend in the bar. The pick fingers supported intermediate the ends of the pick finger support bar are arranged so as to be properly positioned when the pick finger support bar is properly elevated at its ends, and when there is no curvature in the bar. When the bar is bowed downwardly with the clamping action of the prior art assemblies, the pick fingers at the middle portion of the pick finger support bar are supported at an elevation lower than those pick fingers nearer the ends of the bar. The machine operator is therefore required to adjust the pick finger support bar, by loosening the clamps somewhat, or by raising the ends of the bar so that the middle pick fingers better fit about the cylindrical glue applicator roll. Loosening of the support tends to cause the pick finger support bar to be less stable, and readjusting the elevation of the ends of the support bar to properly position the middle pick fingers tends to cause the pick fingers nearer the ends of the support bar to be moved slightly out of their proper positions. In either instance, there is at least some likelihood that the equipment will malfunction.